1. Field of the Invention
The invention relates to a semiconductor device, an LED head, and an image forming apparatus.
2. Description of Related Art
There is a known technique of efficient light extraction in the field of optical semiconductor devices used in such elements as light-emitting elements and light-receiving elements. According to the technique, a layer with high optical reflectance is formed as one of the layers included in the semiconductor device. In the semiconductor device, the light that goes in the direction of the light-extraction surface can be extracted from the light-extraction surface. Besides, the light that goes out in the direction of the backside surface of the semiconductor thin film is reflected by the high-reflective layer and thus can be extracted from the light-extraction surface as well.
The conventional technique makes it possible to extract, out of the light excited in the light emitter, the light going out from the light-emitting region towards the light-extraction surface as well as the light going out from the light-emitting region towards the side opposite to the light-extraction surface and being reflected by the light-reflection layer so as to go out of the light emitter from the light-extraction surface. However, most of the light that goes out from the light-emitting region in directions other than the above-mentioned ones cannot be extracted.